Apparatus for processing ultrasonic image and method thereof

ABSTRACT

An ultrasonic imaging method includes emitting ultrasonic pulses in different directions and acquiring ultrasonic echo signals from an object, calculating an attenuation rate of the ultrasonic echo signals, correcting the acquired ultrasonic echo signals based on the attenuation rate, and outputting the corrected ultrasonic echo signals as an ultrasonic image.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2013-0056982, filed on May 21, 2013 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

Apparatuses and methods consistent with exemplary embodiments relate toan apparatus for processing an ultrasonic image which generates an imageusing ultrasonic signals and a method thereof.

2. Description of the Related Art

An ultrasonic diagnostic apparatus emits ultrasonic waves toward atarget region of an object from the surface of the object and generatesan image of the target region such as a soft tissue tomogram or a bloodstream image using reflected ultrasonic signals, i.e., ultrasonic echosignals.

The ultrasonic diagnostic apparatus is widely used for heart diagnosis,breast diagnosis, celiac diagnosis, urinary diagnosis, and obstetricdiagnosis.

An ultrasonic diagnostic apparatus includes a main body, an ultrasonictransceiver that transmits and receives ultrasonic waves, a controlpanel provided with a variety of switches and keys used to inputcommands for manipulation of the ultrasonic diagnostic apparatus, and adisplay that displays the result of ultrasonic diagnosis using an image.

A process of performing ultrasonic diagnosis using the ultrasonicdiagnostic apparatus is as follows. First, a medical professional suchas a radiologist or a doctor performs ultrasonic imaging by moving theultrasonic transceiver in a state of contacting the surface of the bodyof the object with one hand and manipulating the control panel with theother hand. An ultrasonic image acquired during the ultrasonic imagingis displayed on the display in real time, so that the medicalprofessional may examine the images and provide diagnosis of the object.

Tissues constituting the human body have different reflectivity andabsorption with respect to ultrasonic signals. In an ultrasonicdiagnostic imaging, the composition of materials constituting the humanbody is revealed by analyzing the intensity of ultrasonic wavesreflected from the human body. That is, when ultrasonic waves areemitted to the same medium, reflected ultrasonic waves should have thesame intensity. However, the intensity of ultrasonic waves actuallyreflected by an interface between media varies according to respectiveproceeding directions of the ultrasonic waves and angles of incidence ofthe ultrasonic waves at the interface between media, and thuscharacteristics of the media may be distorted.

SUMMARY

Exemplary embodiments address at least the above problems and/ordisadvantages and other disadvantages not described above. Also, theexemplary embodiments are not required to overcome the disadvantagesdescribed above, and may not overcome any of the problems describedabove.

One or more exemplary embodiments provide an apparatus for processing anultrasonic image capable of correcting intensity of actual reflectedultrasonic waves by emitting a plurality of ultrasonic pulses indifferent directions using spatial division and a method thereof.

In accordance with an aspect of an exemplary embodiment, a method ofprocessing an ultrasonic image includes emitting a plurality ofultrasonic pulses in different directions and acquiring a plurality ofultrasonic echo signals from an object, calculating an attenuation rateof the ultrasonic echo signals, correcting the acquired ultrasonic echosignals based on the attenuation rate, and outputting the correctedultrasonic echo signals as an ultrasonic image.

In accordance with an aspect of an exemplary embodiment, an ultrasonicimage processing apparatus includes an ultrasonic probe emitting aplurality of ultrasonic pulses in different directions and receiving aplurality of ultrasonic echo signals from an object, an attenuation rateobtainer to calculate an attenuation rate of the ultrasonic echosignals, a corrector to correct the acquired ultrasonic echo signalsbased on the attenuation rate, a beamformer to covert the correctedultrasonic echo signals into ultrasonic image signals, and a display tooutput the converted ultrasonic image signals as an image.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will be more apparent by describingcertain exemplary embodiments with reference to the accompanyingdrawings, in which:

FIG. 1 is a perspective view illustrating an apparatus for processing anultrasonic image according to an exemplary embodiment;

FIG. 2 is a control block diagram illustrating an apparatus forprocessing an ultrasonic image according to an exemplary embodiment;

FIG. 3 is a diagram for describing reflectivity according to areflective surface and a proceeding direction of a pulse;

FIG. 4 is a three-dimensional (3D) ultrasonic image of a fetus output bya 3D ultrasonic imaging device;

FIG. 5 is a diagram schematically illustrating emission of ultrasonicpulses to an object using a two-dimensional (2D) array probe;

FIG. 6 is a diagram illustrating a process of emitting ultrasonic pulsesto an object by an ultrasonic probe including one-dimensionally alignedtransducers;

FIGS. 7A and 7B are diagrams illustrating a process of emittingultrasonic pulses to an object by an ultrasonic probe includingtwo-dimensionally arrayed transducers;

FIG. 8 is a diagram illustrating an ultrasonic probe includingtwo-dimensionally arrayed transducers;

FIG. 9 is a flowchart illustrating a method of processing an ultrasonicimage including acquiring ultrasonic echo signals; and

FIG. 10 is a flowchart illustrating a method of processing an ultrasonicimage when four or more ultrasonic echo signals are acquired.

DETAILED DESCRIPTION

Exemplary embodiments are described in greater detail with reference tothe accompanying drawings.

In the following description, like drawing reference numerals are usedfor like elements, even in different drawings. The matters defined inthe description, such as detailed construction and elements, areprovided to assist in a comprehensive understanding of the exemplaryembodiments. However, it is apparent that the exemplary embodiments canbe practiced without those specifically defined matters. Also,well-known functions or constructions are not described in detail sincethey would obscure the description with unnecessary detail.

FIG. 1 is a perspective view illustrating an apparatus for processing anultrasonic image according to an exemplary embodiment. As illustrated inFIG. 1, the ultrasonic image processing apparatus 98 includes a mainbody 100, an ultrasonic transceiver 110 that is an ultrasonic probe, aninput unit 150, a main display 160, and a sub-display 170.

More than one female connector 145 may be provided at one side of themain body 100. A male connector 140 connected to a cable 130 may bephysically coupled to the female connector 145.

A plurality of casters (not shown) may be provided at the bottom of themain body 100 to provide mobility of the ultrasonic image processingapparatus. The plurality of casters may fix the ultrasound imageprocessing apparatus at a particular place, or may allow the ultrasoundimage processing apparatus to be moved in a particular direction.

The ultrasonic probe 110 that contacts the surface of the body of anobject may transmit and receive ultrasonic waves. Particularly, theultrasonic probe 110 may emit a transmission signal received from themain body 100, i.e., an ultrasonic signal, into the body of the objectand receive an ultrasonic echo signal reflected from a particular regionof the object inside the human body so as to transmit the ultrasonicecho signal to the main body 100. One end of the cable 130 may beconnected to the ultrasonic probe 110, and the other end of the cable130 may be connected to the male connector 140. The male connector 140connected to the other end of the cable 130 may be physically coupled tothe female connector 145 of the main body 100.

The input unit 150 may receive an instruction related to operation of anultrasound image generating apparatus. For example, the input unit 150may receive an instruction to select a mode, such as an A-mode(Amplitude mode), B-mode (Brightness mode), and M-mode (Motion mode), oran instruction to initiate ultrasonic diagnosis. The instructions inputthrough the input unit 150 may be transmitted to the main body 100 via awireless or wired communication network.

For example, the input unit 150 may include at least one of a touchpad,a keyboard, a foot switch, and a foot pedal. The keyboard may be ahardware element located at an upper portion of the main body 100. Thekeyboard may include at least one of a switch, a key, a joystick, and atrackball. In another example, the keyboard may also be a softwareelement, such as a graphical user interface. In this case, the keyboardmay be displayed via at least one of the sub-display 170 and the maindisplay 160. The foot switch or the foot pedal may be provided at alower position of the main body 100, and a manipulator may controloperation of the ultrasound image processing apparatus using the footpedal.

A probe holder 120 in which the ultrasonic probe 110 is placed may beprovided near the input unit 150. More than one ultrasonic probe holder120 may be provided. The medical professional may place the ultrasonicprobe 110 in the ultrasonic probe holder 120 for storage when theultrasonic image processing apparatus is not in use.

The sub-display 170 may be provided at the main body 100. FIG. 4illustrates the case in which the sub-display 170 is located above theinput unit 150. The sub-display 170 may display applications related tooperation of the ultrasound image processing apparatus. For example, thesub-display 170 may display, e.g., a menu or guide map for performingultrasonic diagnosis. The sub-display 170 may, for example, take theform of a Cathode Ray Tube (CRT) or a Liquid Crystal Display (LCD).

The main display 160 may be provided at the main body 100. FIG. 4illustrates the case in which the main display 160 is located above thesub-display 170. The main display 160 may display an ultrasonic imageacquired during the ultrasonic diagnosis. The main display 160 may be aCRT or LCD, similar to the sub-display 170. Although FIG. 1 illustratesthe main display 160 as being coupled to the main body 100, the maindisplay 160 may be separable from the main body 100.

Although FIG. 1 illustrates that the ultrasonic image processingapparatus includes both the main display 160 and the sub-display 170,the sub-display 170 might not be used. In this case, applications or amenu displayed on the sub-display 170 may be displayed on the maindisplay 160.

FIG. 2 is a control block diagram illustrating an ultrasonic imageprocessing apparatus according to an exemplary embodiment.

A method of processing an ultrasonic image according to the presentexemplary embodiment will be briefly described with reference to thecontrol block diagram. The ultrasonic probe 110 receives a plurality ofecho ultrasonic waves from an object and converts the echo ultrasonicwaves into ultrasonic echo signals that are electronic signals. Anattenuation rate obtainer 101 calculates an attenuation rate indicatingthe amount of loss from the ultrasonic echo signals actually reflectedfrom the object based on the acquired ultrasonic echo signals. Acorrector 102 corrects the ultrasonic echo signals based on thecalculated attenuation rate, and a beamformer 103 converts the correctedultrasonic echo signals into ultrasonic image signals. A display 160displays the converted ultrasonic image signals on a screen to acquirean image from which distortion caused when a virtual light source islocated on the path of the ultrasonic probe 110 is removed.

Hereinafter, cause and result of the distortion when the object isilluminated by a virtual light source located on the path of theultrasonic probe 110 will be described with reference to FIGS. 3 and 4.

Ultrasonic diagnosis using an ultrasonic image is performed by use ofthe pulse-echo principle. A transducer 109, as an element of theultrasonic probe 110, may generate ultrasonic pulses and includes aplurality of transducers 111. Each of the generated ultrasonic pulsesproceeds at a constant speed until the ultrasonic pulse encounters areflective surface inside the body of the object. When the ultrasonicpulse encounters the reflective surface, a portion of the ultrasonicpulse is reflected therefrom and returns toward an ultrasonic source,and the other portion of the ultrasonic pulse continuously proceeds inthe proceeding direction. The reflective surface is formed at aninterface between two media having different densities, i.e., aninterface between two different tissues. The reflectivity isproportional to a density difference between the two media. Thus, thecomposition of substances constituting the human body may be revealedvia analysis of the reflected ultrasonic waves. The analysis results areused to examine the tissues of the human body and to generate an imagefor utilization during diagnosis.

FIG. 3 is a diagram for describing reflectivity according to areflective surface and a proceeding direction of a pulse. Reflectivityat the reflective surface is obtained as an intrinsic value according tothe density difference between two media. In this regard, the intrinsicvalue according to the density difference between two media is referredto as sound impedance. Thus, when the same ultrasonic waves are emittedto objects formed of the same medium, reflected echo ultrasonic waveshave the same intensity.

However, the intensity of the echo ultrasonic waves reflected from thesame medium may vary. This is because, the amount of the reflectedultrasonic echo signals may be influenced by an angle between anemission direction of the ultrasonic pulse and the reflective surface ofthe object. That is, as the reflective surface of the object is moreperpendicular to the emission direction of the ultrasonic pulse, theamount of the ultrasonic echo signals returning to the ultrasonic sourceincreases. On the other hand, as an angle between the normal vector withrespect to the reflective surface of the object and the emissiondirection of the ultrasonic pulse increases, the amount of theultrasonic echo signals returning to the ultrasonic source decreases.

FIG. 4 is a three-dimensional (3D) ultrasonic image of a fetus output bya 3D ultrasonic imaging device. As described above, since intensities ofultrasonic waves reflected from the same medium vary, distortion iscaused in the ultrasonic image due to such intensity differences. Suchphenomenon is more serious particularly in a three-dimensional (3D)ultrasonic system. In the 3D ultrasonic system, a light source emittinglight in a predetermined direction is set based on volume data, andchange of a 3D image is observed while emitting light in differentdirections. In this case, distortion caused by a virtual light sourcelocated on the path of the ultrasonic probe 110, i.e., an ultrasonicsource, separately from a light source to observe a 3D image, isobtained.

Referring to FIG. 4, an effect as if the fetus would be illuminated atthe front thereof is obtained although lighting is not considered duringrendering. For example, shadows of the forehead, portions near the nose,and portions near the eyes are differently expressed in the image of thefetus, although they are parts of the skin formed of the same medium.This indicates that data is acquired as if the fetus would beilluminated by a light source located on the path of the ultrasonicprobe 110. Such phenomenon does not cause problems while performing abasic rendering process. However, a serious problem may be caused when avirtual light source is introduced and the external appearance of theobject is observed while changing the emission direction thereof.Distortion is caused due to the effect as if the light source would belocated at the position of the ultrasonic probe 110, and thus anunnatural image is acquired. Accordingly, an ultrasonic image with highrealism may be acquired by removing the effect as if the light sourcewould be located at the position of the ultrasonic probe 110.

Hereinafter, an ultrasonic image processing apparatus and a method ofoperating the same to remove distortion from an ultrasonic image will bedescribed in detail.

Referring back to FIG. 2, the ultrasonic probe 110 includes a pluralityof transducers 111 that generate ultrasonic pulses in accordance withsupplied alternating current (AC) power from a power source, emit thegenerated ultrasonic pulses, receive reflected ultrasonic pulses from atarget region of an object, and convert the received echo ultrasonicwaves into electrical ultrasonic echo signals. Here, the power source112 may be an external power supply or an internal capacitor of theultrasonic image processing apparatus.

Various transducers 111 such as a magnetostrictive ultrasonic transducerusing a magnetostrictive effect of a magnetic material, a piezoelectricultrasonic transducer using a piezoelectric effect of a piezoelectricmaterial, a capacitive micromachined ultrasonic transducer (cMUT), whichtransmits and receives ultrasonic waves using vibration of hundreds orseveral thousands of micromachined thin films, may be used.

When alternating current is supplied to the transducers 111 from thepower source 112, piezoelectric vibrators or thin films of thetransducers 111 vibrate, thereby generating ultrasonic pulses. Thegenerated ultrasonic pulses are emitted to the object, for example, ahuman body. The emitted ultrasonic pulse is reflected by at least one ofthe target regions located at various depths in the object. Thetransducers 111 receive echo ultrasonic waves reflected from the targetregion and convert the received echo ultrasonic waves into electricalultrasonic echo signals.

The ultrasonic echo signals are transmitted to the main body 100 via awireless or wired communications network. Since the ultrasonic probe 110receives the echo ultrasonic waves via a plurality of channels, theconverted plurality of ultrasonic echo signals are transmitted to themain body 100 via the channels.

The transducers 111 of the ultrasonic probe 110 may be linear arraytransducers or convex array transducers. The ultrasonic probe 110 may bea two-dimensional (2D) array probe in which the transducers 111 aretwo-dimensionally arrayed.

FIG. 5 schematically illustrates a process of emitting ultrasonic pulsesto the object using a two-dimensional (2D) array probe. The 2D arrayprobe may include two-dimensionally arrayed transducers 111 while havinga similar structure to a general ultrasonic probe. Thus, the pluralityof transducers 111 is disposed on an XY plane. Hereinafter, thetransducers 111 will be described based on locations thereof. Forexample, a column from the left of the X-axis and a row from the top ofthe Y-axis will be used to describe the transducers.

In FIG. 5, bold lines define available display planes. The 2D arrayprobe may acquire 3D image information through electronic irradiationbased on driving time delay of the transducers 111. Particularly, atomogram, i.e., 2D data, of the object such as a plane defined by thebold lines is acquired. The 2D data is collected through the overallsurface of the object by another group of transducers 111 differentlyarrayed. The collected 2D data are accumulated to generate a 3D image inreal time. In addition, since a small-scale ultrasonic probe 110 mayemit ultrasonic waves in a wide range, internal organs such as the heartmay be efficiently irradiated.

FIG. 6 is a diagram illustrating a process of emitting ultrasonic pulsesto an object by an ultrasonic probe including one-dimensionally alignedtransducers. When a plurality of transducers 111 is one-dimensionallyaligned in a linear or convex array, the emission direction ofultrasonic pulses generated by the ultrasonic probe 110 has a 2D vectorform. That is, since the transducers 111 are aligned in a row, there maybe limitation to differently drive the transducers 111 in order tochange the emission direction of the ultrasonic pulses.

FIGS. 7A, 7B, and 8 are diagrams illustrating a process of emittingultrasonic pulses to an object by an ultrasonic probe includingtwo-dimensionally arrayed transducers. As an example of generatingultrasonic pulses having different proceeding directions, a 2D arrayprobe may be used. According to an exemplary embodiment, the pluralityof two-dimensionally arrayed transducers 111 may be divided into aplurality of regions. FIG. 7A illustrates that an ultrasonic pulse isemitted from a region A of the transducers 111 to the object. FIG. 8illustrates that an ultrasonic pulse is emitted from a region B of thetransducers 111 to the object. Arrows from the transducers 111 towardthe object indicate emission directions of the ultrasonic pulse.

As described above, even in the same ultrasonic probe 110, emissiondirections of ultrasonic pulses from the transducers 111 located atdifferent positions may be expressed as 3D vectors, and the 3D vectorsmay have different orientations. That is, the plurality of transducers111 is divided into a plurality of regions, and the regions areindependently driven, so that ultrasonic pulses may be emitted indifferent directions. By use of such characteristics, distortion causedas the location of the ultrasonic probe 110 changes may be efficientlycorrected.

In this regard, the dividing of the transducers 111 into a plurality ofregions may be directly input by a user via the input unit 150 or may bearbitrarily set via internal calculation. Since the normal vectors ofthe surface of the object need to be calculated by acquiring a pluralityof ultrasonic echo signals corresponding to the ultrasonic pulses withdifferent emission directions, the divided regions may be set withoutlimitation.

FIG. 7B is a diagram illustrating an ultrasonic probe includingtwo-dimensionally arrayed transducers divided according to rows.Hereinafter, the present exemplary embodiment will be described based onthe divided transducers 111 by defining a first row as region a,defining a second row as region b, defining a third row as region c, anddefining a fourth row as region d.

The plurality of transducers 111 may be divided into regions a, b, c,and d according to an exemplary embodiment. Arrows indicate emissiondirections of ultrasonic pulses respectively generated by respectivetransducers 111 of the regions a, b, c, and d toward the object. Uponcomparison of the arrows illustrated in FIG. 7B, the emission directionsof the ultrasonic pulses respectively generated in the transducers 111of the regions are different. Here, the ultrasonic pulses are emitted infour different directions, and thus ultrasonic echo signals are alsoacquired in four different directions. When the transducers 111 aregrouped as described above, the same effect as four one-dimensional (1D)array probes emitting ultrasonic pulses toward the object in differentdirections may be obtained.

As described above, even when the ultrasonic probe 110 having a 2D arrayis used, the generated ultrasonic pulses may be emitted in differentdirections, i.e., may have different 3D vectors, according to locationsof the transducers 111. Thus, the generated ultrasonic pulses may beemitted in a plurality of directions. Accordingly, when a plurality ofultrasonic pulses is emitted to the same object in different directionsthrough the 2D array probe and a plurality of ultrasonic echo signalsare received, ultrasonic echo signals similar to the actual reflectedultrasonic echo signals may be acquired through calculation.

According to an exemplary embodiment of the ultrasonic image processingapparatus and a method thereof, a 2D array probe may be used to generateultrasonic pulses having different emission directions. Hereinafter, anexemplary embodiment will be described on the assumption that theultrasonic probe 110 is a 2D array probe.

Referring back to FIG. 2, the ultrasonic probe 110 may generate aplurality of ultrasonic pulses having different emission directions andmay emit the ultrasonic pulses toward the object. In addition, theultrasonic probe 110 may receive a plurality of echo ultrasonic wavesreflected from the object. These processes need to be sequentiallyperformed. Since echo ultrasonic waves reflected from ultrasonic pulsesemitted in one direction may interfere with echo ultrasonic waves ofultrasonic pulses emitted in another direction, the echo ultrasonicwaves acquired from the different directions might not be distinguishedfrom each other. Thus, when the ultrasonic pulses are emitted in a firstdirection, the ultrasonic pulses need to be emitted in a seconddirection after the echo ultrasonic waves from the first direction arereceived.

The ultrasonic probe 110 may emit ultrasonic pulses in differentdirections, three or more directions, from divided regions including thetransducers 111. In a calculation to obtain a normal vector of thesurface of the object, which will be described later, components of thenormal vector may be expressed as a 3D vector with x, y, and zcoordinates. That is, when the ultrasonic pulses are emitted in threedirections, three types of ultrasonic echo signals respectively havingdifferent intensities are acquired, and each component may be obtainedthrough calculation of the matrix. This will be described in detaillater with reference to the attenuation rate obtainer 101.

According to an exemplary embodiment, the main body 100 may include theattenuation rate obtainer 101, the corrector 102, and the beamformer103. The main body 100 may be dispensed with some of the aforementionedconstituent elements.

Referring to FIG. 2, the attenuation rate obtainer 101 may acquireultrasonic echo signals, which are electrical signals converted from theecho ultrasonic waves, from the ultrasonic probe 110. Using the acquiredultrasonic echo signals, the amount of loss from the ultrasonic echosignals actually reflected from the object according to the proceedingdirection, i.e., an attenuation rate of the received ultrasonic echosignals to the actual reflected ultrasonic echo signals may becalculated. The ultrasonic probe 110 receives only some of theultrasonic echo signals actually reflected from the object. Theattenuation rate of the actual reflected ultrasonic echo signals may beused when the corrector 102 corrects the received ultrasonic echosignals into the actual reflected ultrasonic echo signals, which will bedescribed later.

A complex function may be used to calculate the ratio of the receivedecho ultrasonic waves to the actual reflected echo ultrasonic waves.Thus, a Lambertian surface model may be used to simplify thecalculation.

The Lambertian surface model refers to a reflector with a constant speedof light in all directions at a solid angle indicating an object havinga uniform intensity of reflection regardless of angle of view. Accordingto the Lambertian surface model, intensity of reflected light isproportional to the cosine of an angle between the normal vector of thesurface of the object and the emission direction of the light toward theobject. This may be represented by Equation 2.I=I _(E)×cos θ  [Equation 2]

When Equation 2 is applied to the ultrasonic image processing apparatusand the method thereof, I indicates an ultrasonic echo signal receivedfrom the ultrasonic probe 110, I_(E) indicates an actual reflectedultrasonic echo signal, and θ indicates an angle between an emissiondirection of the ultrasonic pulse emitted toward the object and thenormal vector of the surface of the object. Thus, the ratio of thereceived ultrasonic echo signal to the actual reflected ultrasonic echosignal, i.e., attenuation rate of the reflected ultrasonic echo signal,is cos θ. Ultimately, correcting the ultrasonic echo signal acquired byemitting the ultrasonic pulse entails substituting the actual reflectedultrasonic echo signal for the acquired ultrasonic echo signal.

Thus, the normal vector of the surface of the object needs to beobtained before calculating θ. To calculate the normal vector of thesurface of the object, a plurality of ultrasonic pulses to be emitted indifferent directions is generated while fixing the position of theultrasonic probe 110. The ultrasonic probe 110 emits the generatedultrasonic pulses to the object so as to receive echo ultrasonic wavesrespectively corresponding to the ultrasonic pulses. The received echoultrasonic waves are substituted into Equation 2 in a matrix form tocalculate the normal vector of the surface of the object. The normalvector of the surface of the object is calculated using Equation 1below.

$\begin{matrix}{{I_{E} \times \overset{\rightarrow}{N}} = {\begin{pmatrix}\overset{\rightarrow}{L_{1}} \\\overset{\rightarrow}{L_{2}} \\\overset{\rightarrow}{L_{3}}\end{pmatrix} \cdot \begin{pmatrix}I_{1} \\I_{2} \\I_{3}\end{pmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

When Equation 1 is applied to the ultrasonic image processing apparatusand the method thereof, I_(E) indicates an actual reflected ultrasonicecho signal, and {right arrow over (N)} indicates a normal vector of thesurface of the object. In addition, {right arrow over (L₁)}, {rightarrow over (L₂)}, and {right arrow over (L₃)} are unit direction vectorsin the emission direction of the ultrasonic pulses emitted from theultrasonic probe 110 toward the object. I₁, I₂, and I₃ indicateultrasonic echo signals acquired by emitting the ultrasonic pulses.

Equation 1 is rewritten in terms of the normal vector {right arrow over(N)} of the surface of the object, each component of the normal vector{right arrow over (N)} is a function of an ideal ultrasonic echo signalI_(E). In addition, using the normal vector {right arrow over (N)} andthe unit direction vectors {right arrow over (L₁)}, {right arrow over(L₂)}, and {right arrow over (L₃)} in the emission direction of theultrasonic pulse emitted from the ultrasonic probe 110 toward theobject, each having a magnitude of 1, the components of the normalvector {right arrow over (N)} may be calculated.

Three direction vectors of the ultrasonic pulses emitted from theultrasonic probe 110 to the object and three ultrasonic echo signalsacquired by use of the ultrasonic pulses are needed in Equation 1. Thisis because Equation 1 has three unknowns, i.e., x, y, and z componentsof the normal vector {right arrow over (N)} of the surface of theobject. Thus, three equations with the components of the normal vector{right arrow over (N)} of the surface of the object are needed. To thisend, three direction vectors of the ultrasonic pulses emitted from theultrasonic probe 110 to the object and three ultrasonic echo signalsacquired by use of the ultrasonic pulses are substituted into Equation1.

However, the ultrasonic probe 110 may generate direction vectors of theultrasonic pulses having four or more directions and emit the ultrasonicpulses. In this case, since three direction vectors of the ultrasonicpulses and three ultrasonic echo signals acquired by use of theultrasonic pulses are needed in Equation 1, three direction vectors andthree ultrasonic echo signals may be respectively selected from four ormore thereof.

Alternatively, the four or more direction vectors and ultrasonic echosignals are respectively classified into several groups and averages ofthe groups calculated therefrom may be substituted into Equation 1. Byuse of the averages, distortion of an ultrasonic image caused by noisemay be prevented.

In order to calculate the averages of direction vectors and ultrasonicecho signals, various algorithms may be used. Particularly, a least meansquares algorithm may be applied to an ultrasonic image processingapparatus for processing a large amount of data while having a smallcalculation amount. According to the least mean squares algorithm, anultrasonic image may be processed in real time based on high calculationrate. The least mean squares algorithm is well known in the art, andthus a detailed description thereof will not be given.

By use of the normal vector {right arrow over (N)} of the surface of theobject, the angle θ between the normal vector of the surface of theobject and the emission direction of the ultrasonic pulse emitted fromthe ultrasonic probe 110 to the object may be calculated. Thus, cos θacquired by substituting the calculated angle into the cosine functionindicates the attenuation rate of the actual reflected ultrasonic echosignal. Accordingly, the ratio of the received ultrasonic echo signal tothe reflected ultrasonic echo signal may be determined.

Referring back to FIG. 2, the corrector 102 receives the attenuationrate of the actual reflected ultrasonic echo signals acquired by theattenuation rate obtainer 101. The actual reflected ultrasonic echosignals are acquired based on the attenuation rate of the receivedultrasonic echo signals. The corrected ultrasonic echo signals, i.e.,the reflected ultrasonic echo signals, are calculated using Equation 2described above.

The corrected ultrasonic echo signals are values from which virtuallight source effect caused by the position of the ultrasonic probe 110is removed. Thus, the correction process contributes to output anultrasonic image with greater realism than a process of converting thecorrected ultrasonic echo signals into ultrasonic image signalsperformed by the beamformer 103.

The beamformer 103 performs beamforming based on the ultrasonic echosignals corrected by the corrector 102. Beamforming is a process offocusing the ultrasonic echo signals input via a plurality of channelsand acquiring appropriate ultrasonic image signals with respect to theinside of the object.

The beamformer 103 compensates for time difference of ultrasonic echosignals caused distance difference between each of the transducers 111and the target region in the object. Then, the beamformer 103 mayemphasize ultrasonic echo signals from one of the channels andrelatively attenuate ultrasonic echo signals from the other channels soas to focus the ultrasonic echo signals. In this case, the beamformer103 may emphasize or attenuate ultrasonic echo signals from a particularchannel by weighting the ultrasonic echo signals input via each channel.

The beamformer 103 may focus the ultrasonic echo signals acquired by theultrasonic probe 110 at each of a plurality of frames in considerationof the locations of the transducers 111 of the ultrasonic probe 110 anda focus point.

Meanwhile, the beamforming performed by the beamformer 103 may includedata-independent beamforming and adaptive beamforming.

The display outputs the ultrasonic image signals converted by thebeamformer 103 on a screen. The display includes a main display and asub-display and displays data regarding the object on the screen as animage for ultrasonic diagnosis.

FIG. 9 is a flowchart illustrating a method of processing an ultrasonicimage including acquiring ultrasonic echo signals.

A plurality of transducers 111 of the ultrasonic probe 110 is dividedinto a plurality of regions (operation 300). Here, the ultrasonic probe110 is a 2D array probe. A proceeding direction of an ultrasonic pulseis expressed as a 2D vector in the transducer 111 of the 1D array probe.On the other hand, when the transducers 111 of the 2D array probe aredivided into the plurality of regions, an ultrasonic pulse expressed asa 3D vector may be emitted to the same object from each region of thedivided transducers 111. Components of a 3D vector, which are expressedas x, y, and z coordinates, may be efficiently substituted into Equation1.

A process of emitting ultrasonic pulses in different directions and aprocess of acquiring a plurality of ultrasonic echo signals need to besequentially performed. Thus, ultrasonic pulses are emitted from one ofthe divided regions of the transducers 111 (operation 310). Then,ultrasonic echo signals reflected from the emitted ultrasonic pulses areacquired (operation 320). The emission of the ultrasonic pulses andacquisition of the ultrasonic echo signals are performed in the sameregion of the transducers 111.

A next stage is performed after comparing the number of acquiredultrasonic echo signals (operation 330). Since a normal vector of thesurface of the object will be obtained to correct the ultrasonic echosignals by use of Equation 1 in the next stage, three emissiondirections of the ultrasonic pulses and three acquired ultrasonic echosignals are needed.

When, the number of the acquired ultrasonic echo signals is less than 3,ultrasonic pulses are emitted from another region, different from theprevious region, of the divided transducers 111 toward the object(operation 340). Accordingly, ultrasonic echo signals are additionallyacquired. However, when the number of the acquired ultrasonic echosignals is less than 3, a next stage will be performed.

When it is confirmed that three ultrasonic echo signals are acquired,these values are substituted into Equation 1 so as to obtain the normalvector of the surface of the object (operation 350). Specific values ofeach component of the normal vector are acquired by simplifying eachcomponent of the normal vector according to Equation 1 and using thefact that the sizes of the normal vector and the unit direction vectorsin the emission direction of the ultrasonic pulses are 1.

By use of the acquired normal vector, the acquired ultrasonic echosignals are corrected to be similar to the actual reflected ultrasonicecho signals (operation 360). Particularly, an angle between the normalvector of the surface of the object and the emission direction of theultrasonic pulse emitted toward the object is obtained. The obtainedangle is substituted into the cosine function to calculate theattenuation rate of the actual reflected ultrasonic echo signals.Finally, the attenuation rate is substituted into Equation 2 tocalculate the ultrasonic echo signals actually reflected from theobject. The actual reflected ultrasonic echo signals are correctedultrasonic echo signals.

After the ultrasonic echo signals are appropriately corrected, thebeamformer 103 converts the corrected ultrasonic echo signals intoultrasonic image signals (operation 370). The converted ultrasonic imagesignals are signals from which the virtual light source effect in adirection from the ultrasonic probe 110 is removed. Thus, an image withhigh realism may be generated.

FIG. 10 is a flowchart illustrating a method of processing an ultrasonicimage when four or more ultrasonic echo signals are acquired.

A plurality of transducers 111 of a 2D array probe is divided into aplurality of regions, and ultrasonic pulses may be respectively emittedfrom the regions. Emitting the ultrasonic pulses from different regionsof the transducers 111 indicates that the ultrasonic pulses are emittedin different directions. A plurality of ultrasonic echo signalscorresponding to the emission directions changed as described above isacquired (operation 400).

Upon comparison of the number of acquired ultrasonic echo signals asdescribed above, it is determined whether the process enters into a nextstage. That is, when the number of the acquired ultrasonic echo signalsis less than N, the aforementioned process is repeated in order toadditionally acquire the ultrasonic echo signals (operation 400).However, when the number of the acquired ultrasonic echo signals is N orgreater, the process enters the next stage.

Here, N is a natural number of 4 or more. It has been described abovethat three values are needed to calculate the 3D normal vector of thesurface of the object. In addition, when four or more ultrasonic echosignals are acquired, three values need to be selected or averages needto be calculated. Hereinafter, a method of correcting the ultrasonicecho signals using averages of four or more ultrasonic echo signals willbe described.

N may be input by the user via the input unit 150 or may be selected viacalculation of the apparatus.

When the number of the acquired ultrasonic echo signals is N or greater,an average thereof is calculated to remove noise (operation 420). Sincethree equations may be derived from Equation 1, three unit directionvectors in the emission direction of the ultrasonic pulses and threeultrasonic echo signals may be respectively substituted thereinto. Thus,by reducing four or more data into three values by averaging, data closeto the real values may be substituted into Equation 1.

Thus, averages of the acquired ultrasonic echo signals and the directionvectors in the emission direction of the ultrasonic pulse arecalculated. For example, the averages may be calculated using a leastmean squares algorithm. The least mean squares algorithm is well knownin the art, and thus a detailed description thereof will not be given.

The averages of the acquired ultrasonic echo signals and the directionvectors in the emission direction of the ultrasonic pulse aresubstituted into Equation 2 so as to calculate a normal vector of thesurface of the object (operation 430). Three averages of the ultrasonicecho signals acquired according to the ultrasonic image processingapparatus and the method thereof may be substituted thereinto, or oneaverage and two measured values may be substituted thereinto.

The ultrasonic echo signals are corrected using the normal vector of thesurface of the object (operation 440). When the angle between the normalvector and the emission direction of the ultrasonic pulse is calculatedand substituted into the cosine function, the attenuation rate of theactual reflected ultrasonic echo signals may be obtained. Thus, theultrasonic echo signals are corrected by calculating the actualreflected ultrasonic echo signals based thereon and replacing theacquired ultrasonic echo signals with the actual reflected ultrasonicecho signals.

The corrected ultrasonic echo signals are converted into ultrasonicimage signals by the beamformer 103 (operation 450). When the convertedultrasonic image signals are output to the screen through the display, auser may confirm an ultrasonic image from which the effect, in which avirtual light source is located in a direction from the ultrasonic probe110, is removed. Thus, an ultrasonic image of the object with highrealism may be output through the correction process.

According to the ultrasonic image processing apparatus and the methodthereof, errors caused by reflectivity difference in accordance with theposition of the probe may be reduced. Accordingly, a density closer tothe intrinsic density of the medium may be acquired using the same. As aresult, accuracy may be increased in ultrasonic diagnosis.

This may be efficiently applied to an ultrasonic image output when theobject is viewed in a particular direction or 3D ultrasonic diagnosisthrough which cross-sections of the object are reorganized and observed.

The foregoing exemplary embodiments and advantages are merely exemplaryand are not to be construed as limiting. The present teaching can bereadily applied to other types of apparatuses. Also, the description ofthe exemplary embodiments is intended to be illustrative, and not tolimit the scope of the claims, and many alternatives, modifications, andvariations will be apparent to those skilled in the art.

What is claimed is:
 1. An ultrasonic imaging method comprising:sequentially emitting by each transducer group of respective regions,into which a plurality of transducers of an ultrasonic probe aredivided, focused ultrasonic pulses to a same focal point of an object ina first sequential manner; sequentially acquiring, by each transducergroup, ultrasonic echo signals reflected from the same focal point ofthe object in correspondence to the sequentially emitted ultrasonicpulses, in a second sequential manner; calculating, via a processor ofan ultrasound apparatus, a normal vector of a surface of the objectusing emission directions of the focused ultrasonic pulses emitted by atleast three of the transducer groups and intensities of the acquiredultrasonic echo signals in correspondence to the focused ultrasonicpulses emitted by the at least three of the transducer groups;calculating, via the processor, an attenuation rate of the acquiredultrasonic echo signals using the calculated normal vector and emissiondirections of the focused ultrasonic pulses emitted by the at leastthree of the transducer groups, and correcting the acquired ultrasonicecho signals based on the attenuation rate; beamforming the ultrasonicecho signals, an attenuation of which has been corrected, intoultrasonic image signals; and outputting, on a display, the ultrasonicimage signals as an ultrasonic image, wherein the attenuation rate isdirectly proportional to the intensity of the acquired ultrasonic echosignals, and is independent of a depth of focus.
 2. The method accordingto claim 1, wherein the ultrasonic probe comprises a two-dimensional(2D) array probe.
 3. The method according to claim 2, wherein theplurality of transducers are divided into the regions so thattransducers of the plurality of transducers, disposed in a same rowbelong to a same transducer group.
 4. The method according to claim 2,wherein the plurality of transducers are divided into three or moreregions to emit the ultrasonic pulses in three or more emissiondirections.
 5. The method according to claim 4, wherein the attenuationrate is a cosine of an angle between the normal vector of the surface ofthe object and an emission direction vector of the ultrasonic pulses. 6.The method according to claim 5, wherein the ultrasonic pulses areemitted in four or more directions, and the calculating the normalvector of the surface of the object comprises calculating the normalvector of the surface of the object by using averages of emissiondirection vectors of the ultrasonic pulses and averages of the acquiredultrasonic echo signals.
 7. The method according to claim 6, wherein thecorrecting the acquired ultrasonic echo signals is performed usingEquation 2:I=I _(E)×cos θ  [Equation 2] wherein I is the intensity of the acquiredultrasonic echo signal, I_(E) is the intensity of actual reflectedultrasonic echo signal, and θ is an angle between the ultrasonic pulseand the normal vector of the surface of the object.
 8. An ultrasonicimage processing apparatus comprising: an ultrasonic probe comprising aplurality of transducers which are divided into regions for formingtransducer groups, each of the transducer groups being configured tosequentially emit focused ultrasonic pulses to a same focal point of anobject in a first sequential manner and sequentially acquire echosignals reflected from the same focal point of the object in a secondsequential manner; a processor configured to calculate a normal vectorof a surface of the object using emission directions of the focusedultrasonic pulses emitted by at least three of the transducer groups andintensities of the acquired ultrasonic echo signals in correspondence tothe focused ultrasonic pulses emitted by the at least three of thetransducer groups, calculate an attenuation rate of the acquiredultrasonic echo signals using the calculated normal vector and emissiondirections of the focused ultrasonic pulses emitted by the at leastthree of the transducer groups, and correct the acquired ultrasonic echosignals based on the attenuation rate; a beamformer configured toconvert the ultrasonic echo signals, an attenuation of which have beencorrected, into ultrasonic image signals; and a display configured tooutput the ultrasonic image signals as an image, wherein the attenuationrate is directly proportional to the intensity of the acquiredultrasonic echo signals, and is independent of a depth of focus.
 9. Theultrasonic image processing apparatus according to claim 8, wherein theplurality of transducers of the ultrasonic probe comprisestwo-dimensionally arrayed transducers.
 10. The ultrasonic imageprocessing apparatus according to claim 9, wherein the two-dimensionallyarrayed transducers are divided into the regions so that transducers ofthe plurality of transducers, disposed in a same row belong to a sametransducer group.
 11. The ultrasonic image processing apparatusaccording to claim 9, wherein the plurality of transducers are dividedinto three or more regions to emit the ultrasonic pulses in three ormore emission directions.
 12. The ultrasonic image processing apparatusaccording to claim 11, wherein the attenuation rate is a cosine of anangle between the normal vector of the surface of the object and anemission direction vector of the ultrasonic pulses.
 13. The ultrasonicimage processing apparatus according to claim 12, wherein the ultrasonicpulses are emitted in four or more directions, and the processor isfurther configured to calculate the normal vector of the surface of theobject using averages of emission direction vectors of the ultrasonicpulses and averages of the acquired ultrasonic echo signals.
 14. Theultrasonic image processing apparatus according to claim 13, wherein theprocessor is configured to correct the acquired ultrasonic echo signalsusing Equation 2:I=I _(E)×cos θ  [Equation 2] wherein I is the intensity of the acquiredultrasonic echo signal, I_(E) is the intensity of the actual reflectedultrasonic echo signal, and θ is an angle between the ultrasonic pulseand the normal vector of the surface of the object.